Garmin Fit is a US$0.99 iPhone app that is used as a training tool for walking or cycling. The app uses GPS to keep track of your exercise stats, like speed, distance traveled, route traveled and an estimate of calories burned. This data can be uploaded to GarminConnect, a web-based service. The app also allows you to select music that is on your iPhone to accompany you while you exercise.
With the latest update to the app, Garmin has added Live Track (available as an in-app purchase), which allows you to send a 'follow me' invitation to others via email, Facebook or Twitter. They'll get a link that lets them monitor your elapsed time, distance, speed, elevation and more. Just the thing to let someone virtually participate with you while you are on that run or marathon. Live Track can be had for $20 per year or $1.99 per month.
Reviews of the previous version of the app are mixed, with some people complaining about stability and issues with multi-tasking. I think the cost of Live Track is too high. $20.00 per year as an add-on to an app that's only $0.99 is a bit too much. You can go with Live Track monthly for $1.99, but again, that's twice the cost of the app for one month of use.
Garmin Fit is a good idea, but a bit flawed in execution and price of the add-ons. Live Track is a good idea for regular racers, but some free apps like Glympse will let you share your location, without some of the bells and whistles Garmin provides.